Cloth simulation doesn't work for particular object
I had the same problem. Took me over half an hour to figure out.
The problem is caused by duplicated vertices.
To fix it switch to edit mode.
Press Alt + H to make sure there is nothing hidden. Then select all vertices A and then press M to merge them by distance.
Have a look at the status bar: 148 vertices removed. Switch back to object mode. Play the simulation. It works again.